This invention relates to a new and improved detector for determining the location (position) of deposition substrates (wafers) as they are being transported from one point to another in a high vacuum RF and DC sputtering system.
High vacuum sputtering systems for the deposition and/or etching of material on a wafer in the manufacture of integrated circuits are well known. Such a system typically comprises a first airlock loading chamber in which cassettes containing a plurality of wafers to be processed are placed and from which the wafers are transported through a second vacuum chamber or transportation chamber by any suitable conveyor and are then placed on a rotating table or stage within the sputtering chamber. In this chamber the wafers to be processed are rotated in the presence of RF or DC voltage for the deposition or etching of material on the wafer. After the sputter processing, the processed wafers are again transported back through the transportation chamber and into the loading chamber and into the cassette to be removed for further handling/processing.
For the proper operation of the system, it is necessary to provide the microprocessor, which controls the system's operation, with accurate information regarding the location, presence or absence, of wafers along the path between the loading chamber and sputtering chamber. In order to do this, any wafer detector must operate in high vacuum and in a high voltage DC and RF environment. To those skilled in the art, it will be clear that the detector, or more specifically the transducer, selected must not "outgas" under conditions of high vacuum, and not only the transducer but its associated circuitry must function in this DC and RF environment.